Device and method for cutting out contours from planar substrates by means of laser

ABSTRACT

The present invention relates to a method for producing a contour in a planar substrate and for separating the contour from the substrate, in particular for producing an internal contour in a planar substrate and for removing the internal contour from the substrate, wherein, in a contour definition step by means of a laser beam guided over the substrate along a contour line characterising the contour to be produced, a large number of individual zones of internal damage is produced in the substrate material, in a crack definition step by means of a laser beam guided over the substrate along a plurality of crack line portions, which, viewed from the contour line, leads away at an angle a &gt;0° , and into the contour to be separated, respectively a large number of individual zones, . . . ) of internal damage is produced in the substrate material and, in a material removal step implemented after the contour definition step and after the crack definition step by means of a material-removing laser beam guided over the substrate along a material removal line which extends along the contour line but at a spacing from the latter and also in the contour to be separated, furthermore which preferably cuts the crack line portions, the substrate material is removed over the entire substrate thickness.

The present invention relates to a device and to a method for cuttingout contours from planar substrates (in particular: from glasssubstrates or crystal substrates) by means of laser.

DE 10 2011 00768 A1 describes how, with the help of a laser,semiconductor wafers, glass elements and other substrates can be dividedinto various parts by the wavelength of the laser being greatly absorbedby the material. As a result, material removal which leads finally todivision of the substrate into a plurality of parts is effected.However, this method has disadvantages in the case of many materials,such as for example impurities due to particle formation during ablationor cut edges which have undesired microcracks or melted edges so that acut gap which is not uniform over the thickness of the material isproduced. Since in addition material must be vaporised or liquefied, ahigh average laser power must be provided.

Starting from the state of the art, it is therefore the object of thepresent invention to make available a method (and also a correspondingdevice) with which planar substrates, in particular made of brittlematerials, can be machined with minimum crack formation at the edges,with as straight as possible cut edges and at a high process speed suchthat contours can be machined out from these substrates (and finallyseparated) without the result being undesired cracks, flaking or otherdisruptions which extend in the substrate plane remaining in thesubstrate after separation of the contours. Hence the aim of the presentinvention is exact, clean separation of a contour from a substrate, inparticular clean, precise removal of internal contours from thesubstrate.

As is described subsequently in detail also, the operation takes place,according to the invention, generally with a pulsed laser at awavelength for which the substrate material is essentially transparent.However, basically also the use of a continuous-wave laser is possibleprovided that the laser beam can be switched rapidly on and off againduring guidance thereof over the substrate surface (e.g. by means of anoptical modulator) in order to produce zones of internal damage situatedone behind the other (see subsequently).

The object according to the invention is achieved by a method accordingto claim 1 and also by a device according to claim 16, advantageousvariants being described in the dependent claims.

Subsequently, the invention is first described in general, then withreference to embodiments. The features according to the inventionproduced within the scope of the embodiments need not thereby beproduced precisely in the illustrated combinations within the scope ofthe invention but rather individual features can also be omitted orcombined with other features in a different way. In particular, alsofeatures of different embodiments can be combined with each other orindividual ones of the illustrated features can also be omitted.

The essential features of the method according to the invention aredescribed in claim 1. The contour is thereby understood as atwo-dimensional surface in the substrate plane in the form of a partialsurface of the substrate. The portions of the substrate corresponding tothis partial surface are intended to be removed from the substrate, theremaining portions of the substrate being intended to be furtherprocessed in subsequent processes. In other words: the contour to beseparated from the substrate forms an undesired surface which can alsobe destroyed, the remaining substrate portions are intended to survivethe separation process of the contour without internal damage and alsowith as ideal cut edges as possible according to the contour line. Thisis achieved according to the invention. Subsequently, there is/arethereby understood by the substrate, both the still unmachined substratebefore separation of the contour and the remaining substrate remainsafter the separation of the contour. From the context respectively, theperson skilled in the art knows what is intended.

According to the invention, the contour definition step is effected suchthat, after implementation thereof, the contour course of the contour isinscribed into the substrate material, however the contour is stillconnected to the substrate so that complete separation of the contourfrom the substrate is still not effected: the step-wise completeseparation of the undesired contour from the substrate is effected bythe contour definition step, the optional crack definition step, theoptional stress-relieving step and the material removal- and/or materialdeformation step and, provided still required (i.e. if the contourremains do not independently already fall off by means of intrinsicstresses in the material after implementing steps (a) to (d)), by anoptional aftertreatment step. Also the introduction of the individualzones of internal damage in the optional crack definition step (cf.claim 4) and in the optional stress-relieving step is effected such thatcomplete separation of the consequently produced partial portions in thesubstrate is still not effected.

Implementation of the optional crack definition step is effectedpreferably after conclusion of the contour definition step but this isnot necessary: thus for example also partial portions of the contourline can be produced firstly by introducing the zones of internal damagebefore the crack definition step for producing the crack line portionsis implemented and, after conclusion of the same, the remaining contourline portions of the contour definition step are introduced into thesubstrate material.

There is understood by the term of a crack line portion leading awayfrom the contour line at an angle α>0°, that the angle a between thelocal tangent to the contour line at that place where the mentioned(possibly continued towards the contour line) crack line portion leadsaway from the contour line, and the local tangent at that end of thecrack line portion, which is orientated towards the contour line, isgreater than 0°.

According to the invention, the laser irradiation in steps (a), (b) and(d) (i.e. in the contour definition step, in the crack definition stepand in the stress-relieving step—subsequently these terms (a) to (d) arealso used alternatively for the steps according to the invention) neednot be effected perpendicular to the substrate plane, i.e. theindividual zones of internal damage need not extend perpendicular to thesubstrate plane (and also need not definitely pass through the entiresubstrate thickness perpendicular to the substrate plane). The laserirradiation can be effected also at an angle >0° (for example between 0°and 20°) relative to the substrate normal (inclined introduction of thezones of internal damage).

There are understood by the internal contours machined preferably withinthe scope of the invention (i.e. to be introduced and removed) simplycoherent quantities of the two-dimensional space (plane of thesubstrate) or corresponding partial portions in the substrate, from amathematical point of view. The internal contours to be removedtherefrom can thereby have almost any shapes. In particular, circularshapes, ellipse shapes, pin-cushion shapes, oblong shapes (with roundedcorners) etc. are possible for the internal contours, by the laser beambeing moved on the substrate surface along a correspondingly shapedcontour line. Preferably, the substrate is disposed thereby in astationary manner within the world coordinate system and the laser beamis moved over the substrate surface by a suitable beam-guiding opticalunit (which can have for example an F-theta lens followed by agalvanometer scanner). Alternatively, also a beam-guiding lens systemwhich is stationary relative to the world coordinate system is possible,the substrate then requiring to be moved in the world coordinate systemrelative to the beam-guiding lens system and to the laser beam.

There is understood subsequently by substrate thickness, the extensionof the substrate perpendicular to the substrate plane, i.e. betweensubstrate front-side and the substrate rear-side. The substratefront-side is thereby that surface of the substrate which is orientatedtowards the radiated laser light.

The first preferably achieved features of the method according to theinvention (material removal for introduction of a removal line) can bededuced from claim 2.

This material removal can be applied in particular to large and smallradii of internal contours to be separated and is suitable in particularfor smaller contours, such as e.g. sections of a circle with a diameter<2.5 mm and for oblong holes.

For the material removal, a CO₂ laser with a beam diameter of in therange between approx. 0.05 mm and 0.5 mm, when impinging on thesubstrate (achieved by focusing) can be used. The CO₂ laser can bepulsed or applied continuously. Preferably, pulses in the range of 100μs to 4,000 μs are used with pulse train frequencies of 0.1 kHz to 100kHz. For particular preference, the pulse duration is in the rangebetween 300 μs and 4,000 μs with 0.1 kHz to 3 kHz pulse train frequency.The laser power can be in the range of 10 to 200 W, preferably howeverin the range of 10 to 100 W.

The travel path of the laser beam is along the contour line, at aspacing from this and in the contour to be separated, for exampletherefore on a (parallel) trajectory symmetrical to the target contour.For example with a circular contour to be removed (hole section), acircular movement. The travel path can be performed either once or withmultiple repetition.

Due to the small focus diameter and the high laser powers, the substratematerial is primarily melted (material removal). Together with laserpulses in the upper microsecond range, the entire substrate materialthickness (e.g. 0.7 mm) can thus be heated through completely with onepulse.

The material removal step can be assisted by the use of a gas nozzlewith process gas (e.g. CDA). With for example a nozzle diameter of 2 mmand gas pressures of 1.5 to 4 bar, material removal can be producedparticularly well even for small contours and radii. By means of the gasflow, the material melted by the laser is expelled in the beamdirection.

With the above-described parameters, for example also toughened glasses(DOL 40 μm) can be supplied for material removal without the resultbeing damaging crack formation.

The removal contour (removal line) should be removed sufficiently farfrom the contour line (target contour cut) (generally, spacings here ofapprox. 0.1 to 0.3 mm suffice, according to the substrate material): forexample with a circular glass disc of 2 mm diameter which is to beremoved, the minimum spacing of the removal line from the contour lineshould be 0.1 mm (deformation diameter or diameter of the circularremoval line at most 1.8 mm). In the case of a glass sheet diameter of1.5 mm, the deformation diameter should be at most 1.3 mm. In the caseof a glass disc diameter of 1.0 mm, the deformation diameter should beat most 0.8 mm.

The crack line portions (e.g. V-cuts) which are described subsequentlyin more detail have an assisting effect for the complete separation ofthe contour.

According to the advantageous features of claim 3, instead of one, or inaddition to a material removal according to claim 2, also removal ofmaterial portions of the contour to be separated is possible by means ofthermal deformation.

A CO₂ laser or the laser beam thereof for extraction of substratematerial in a manner which does not remove substrate material, i.e canbe used in a purely thermally deforming manner in substrate material (inparticular of the contour to be separated) (this is effected preferablyin the case of fairly large contours to be separated, e.g. in the caseof circular sections with a diameter ≧2.5 mm, preferably ≧5-10 mm, to beseparated).

The procedure with such a material deformation step can be as follows:

By means of CO₂ laser irradiation of the substrate, e.g. by means ofmovement of the laser beam along the contour line but at a spacingtherefrom and also in the contour to be separated (for example along acircle or a spiral in the centre of the contour to be separated), atleast portions of the contour to be separated are heated such that theresult is a plastic deformation of at least portions of the contour tobe separated. The diameter of the CO₂ laser spot impinging on thesubstrate material can cover a wide range: 0.1 mm to 10 mm. A diameterof 0.2 mm to 3 mm is preferred. The CO₂ laser can be operated bothpulsed and continuously. Preferably, however, pulses in the range of 6μs to 4,000 μs are used with pulse train frequencies in the range of 0.1kHz to 100 kHz. The laser power can be in the range between 10 and 300W, preferably in the range between 10 and 50 W.

The travel path of the laser is preferably a trajectory which issymmetrical (e.g. parallel, but at a spacing) relative to the contour tobe separated (target contour). For example in the case of a hole sectionas internal contour to be separated, a circular movement. However aspiral movement can also have a favourable effect on the thermoplasticdeformation of such an internal contour (e.g. glass disc). In certaincases, it can prove to be favourable if the laser beam remainsstationary over a defined time interval of for example between . . . sand 0.5 s simply in the centre of the contour to be separated and heatsthrough and thus deforms the contour to be separated. The travel pathcan be covered either once or with multiple repetition which can have afavourable effect on the thermoplastic deformation of the contour to beseparated.

The plastic deformation in the centre leads to shrinkage of the contourto be separated (e.g. glass disc) due to a thermally-induced flow of thesubstrate material (e.g. glass material) in the irradiated region in thecentre and towards the centre. For example in the case of a circulardisc as contour to be separated, this can be seen as follows:

-   -   The deformation generally forms, as a result of gravity, a bulge        away from the laser in the direction of the centre of the earth.        This bulge possibly can adopt a drop shape. The surface        topography can be compared with that of a convex lens.    -   Under specific laser conditions, a bulge is also formed towards        the laser. The surface topography is then that of a biconvex        lens.    -   Under specific laser conditions, a dent (concave) is formed on        one side and, on the opposite surface, a bulge.    -   If the irradiated surface is subjected to a flow of process gas        (commercial air, CDA) in parallel and contemporaneously via a        gas nozzle, the formation of the bulge and/or dent can be        controlled very precisely. As a result, even contours with very        small radii (<2.5 mm to 1.2 mm) can be introduced for the        removal. In the case of for example a nozzle diameter of 2 mm        and gas pressures in the range of 1.5 to-3 bar, relatively small        contours can be particularly readily removed.

What the described thermoplastic deformation variants have in common isthat substrate material of the contour to be separated flows (e.g. inthe case of an internal contour to be removed flows towards the centreof the same) and consequently a gap relative to the remaining substratematerial is formed (e.g. externally situated material of an internalcontour to be removed). Such a gap can have dimensions of approx. 10 μmto 50 μm.

After a short thermal relaxation time (cooling and shrinkage of thecontour to be separated), the contour to be separated falls out purelydue to the forming gap.

In the case of the material deformation step, hence no substratematerial is removed, no removal products are produced.

The CO₂-induced thermoplastic deformation or the regions irradiated bythe laser should be removed sufficiently far (generally spacings ofapprox. 1 to 3 mm suffice according to the substrate material) from thealready introduced contour line (contour cut): for example with a glassdisc of 10 mm diameter to be removed, the region irradiated centrally inthis glass disc (deformation diameter) should have a diameter of 8 mm atmost. In the case of a glass disc diameter of 5 mm, this region shouldbe 3.4 mm at most. In the case of a glass disc diameter of 2.5 mm, thisregion should be 1.5 mm at most.

The already introduced contour line (target contour cut) forms asufficient thermal insulation relative to the surrounding material ofthe residual, remaining substrate so that, with suitable thermoplasticdeformation diameter, no disadvantageous thermal effect on the cut edgeor on the surrounding material in the form of chipping or parasiticcrack formation can be effected.

In the subsequent embodiments, the material removal-and/or materialdeformation step as material removal step is effected by means amaterial-removing laser beam which is not illustrated in more detail.

Further preferably produced features can be deduced from claims 4 to 6.

The ultrasonic treatment according to claim 6 can be effected asfollows: frequency range between 1 kHz and 50 kHz (particularlypreferred: 5 kHz-40 kHz). The surface in the interior of the cut contour(i.e. in the contour to be separated) is thereby preferably contactedwith an ultrasonic actuator. The contact surface can thereby correspondto the dimensions and the shape of an internal contour to be separated.The contact can be implemented over the entire surface or as a ring. Ina particular embodiment, substrate regions situated outside the contourto be separated can be treated with ultrasound (also simultaneousultrasound treatment of the contour to be separated and such remainingsubstrate regions is possible).

A corresponding aftertreatment step is however frequently not requiredat all since the zones of internal damage, which are introduced in step(b) (and in the possibly implemented optional step (d)) already haveinternal stresses introduced into the substrate material which sufficefor the undesired contour remains to be detached by themselves from theremaining substrate (self-removal of the contour remains) in the courseof the material removal-and/or material deformation step or after thesame.

Further advantageous achievable method features can be deduced fromclaim 7 and claim 8.

All of the already described advantageous features and of thesubsequently also described advantageous features can be producedthereby, within the scope of the invention, respectively individually oralso in any combinations with each other.

The point focusing described in claim 8 can thereby be implemented asdescribed in U.S. Pat. No. 6,992,026 B2 or in WO 2012/006736 A2.

According to the invention, it is however particularly preferred tointroduce the individual zones of internal damage along the contourline, the crack-line portions and possibly also the stress-relievingline portions by means of the laser beam focal line described in claim 8(i.e. by induced absorption in the substrate material along an extendedportion in the thickness direction of the material).

This preferred embodiment of step (a), (b) and (d) is now describedsubsequently in detail.

Firstly, it is thereby essential that the wavelength of the irradiatinglaser is chosen in coordination with the substrate to be machined suchthat the substrate material is essentially transparent for this laserwavelength (see also claim 11).

The method for steps (a), (b) and (d) produces a laser focal line perlaser pulse (in contrast to a focal point) by means of a laser lenssystem which is suitable for this purpose (subsequently also termedalternatively beam-guiding optical unit or optical arrangement). Thefocal line determines the zone of interaction between laser and materialof the substrate. If the focal line falls into the material to beseparated, then the laser parameters can be chosen such that aninteraction with the material takes place and produces a crack zonealong the focal line. Important laser parameters here are the wavelengthof the laser, the pulse duration of the laser, the pulse energy of thelaser and possibly also the polarisation of the laser.

For the interaction of the laser light with the material in steps (a),(b) and (d), there should preferably be the following:

1) The wavelength 1 of the laser is preferably chosen such that thematerial is essentially transparent at this wavelength (for example inconcrete terms: absorption <<10% per mm material depth =>γ<<1/cm; γ:Lambert-Beer absorption coefficient).

2) The pulse duration of the laser is preferably chosen such that,within the interaction time, no substantial heat transport (heatdiffusion) from the interaction zone can take place (for example inconcrete terms: τ<<d²/α, d: focal diameter, τ laser pulse duration, α:heat diffusion constant of the material).

3) The pulse energy of the laser is chosen preferably such that theintensity in the interaction zone, i.e. in the focal line, produces aninduced absorption which leads to local heating of the material alongthe focal line, which in turn leads to crack formation along the focalline as a result of the thermal stress introduced into the material.

4) The polarisation of the laser influences both the interaction on thesurface (reflectivity) and the type of interaction within the materialduring the induced absorption. The induced absorption can take place viainduced, free charge carriers (typically electrons), either afterthermal excitation or via multiphoton absorption and internalphotoionisation or via direct field ionisation (field strength of thelight breaks the electron bond directly). The type of production of thecharge carriers can be assessed for example via the so-called Keldyshparameter (reference) which however plays no role in the application ofthe method according to the invention. In the case of specific (e.g.double-refracting materials), it can be important merely that thefurther absorption/transmission of the laser light depends upon thepolarisation and hence the polarisation should be chosen favourably viasuitable lens systems (phase plates) by the user for separation of therespective material, e.g. simply in a heuristic manner. If the substratematerial is therefore not optically isotropic but for exampledouble-refracting, then also the propagation of the laser light in thematerial is influenced by the polarisation. Therefore the polarisationand the orientation of the polarisation vector can be chosen such that,as desired, only one focal line and not two thereof are formed (ordinaryand exraordinary beams). This is of no importance in the case ofoptically isotropic materials.

5) Furthermore, the intensity should be chosen via the pulse duration,the pulse energy and the focal line diameter such that no ablation ormelting but only crack formation in the structure of the solid body iseffected. This requirement can be fulfilled for typical materials, suchas glass or transparent crystals, most easily with pulsed lasers in thesub-nanosecond range, in particular therefore with pulse durations ofe.g. between 10 and 100 ps. Above scale lengths of approx. onemicrometre (0.5 to 5.0 micrometres), the heat conduction for poor heatconductors, such as for example glasses, acts into the sub-microsecondrange, whilst, for good heat conductors, such as crystals andsemiconductors, the heat conduction is effective even from nanosecondsonwards.

The essential process for forming the zones of internal damage, i.e. thecrack formation in the material which extends vertically relative to thesubstrate plane, is mechanical stress which exceeds the structuralstrength of the material (compression strength in MPa). The mechanicalstress is achieved here by rapid, non-homogeneous heating (thermallyinduced stress) due to the laser energy. The crack formation in steps(a), (b) and (d), provided there is corresponding positioning of thesubstrate relative to the focal line (see subsequently), of coursestarts on the surface of the substrate since the deformation is greatestthere. This is because, in the half-space above the surface, there is nomaterial which can absorb forces. This argument also applies formaterials with toughened or prestressed surfaces as long as thethickness of the toughened or prestressed layer is large relative to thediameter of the suddenly heated material along the focal line (see, inthis respect, also FIG. 1 which is also described subsequently).

The type of interaction can be adjusted via the fluence (energy densityin joules per cm²) and the laser pulse duration with the chosen focalline diameter such that firstly no melting takes place on the surface orin the volume and secondly no ablation takes place with particleformation on the surface.

Subsequently, the production of the contour line of a desired separationsurface (relative movement between laser beam and substrate along thecontour line on the substrate surface), i.e. step (a), is described. Thesame applies to (b) and (d).

The interaction with the material produces, per laser pulse, anindividual, continuous (viewed in the direction perpendicular to thesubstrate surface) crack zone in the material along a focal line. Forcomplete separation of the material, a sequence of these crack zones perlaser pulse is placed so closely to each other along the desiredseparation line that a lateral connection of the cracks to form adesired crack surface/contour is produced in the material. For this, thelaser is pulsed at a specific train frequency. Spot size and spacing arechosen such that, on the surface along the line of the laser spots, adesired, directed crack formation begins. The spacing of the individualcrack zones along the desired separation surface is produced from themovement of the focal line relative to the material within the timespanof laser pulse to laser pulse. See in this respect also FIG. 4 which isalso described subsequently.

In order to produce the desired contour line or separation surface inthe material, either the pulsed laser light can be moved with an opticalarrangement which is moveable parallel to the substrate plane (andpossibly also perpendicular thereto) over the stationary material or thematerial itself is moved past the stationary optical arrangement with amoveable receiving means such that the desired separation line isformed. The orientation of the focal line relative to the surface of thematerial, whether perpendicular or at an angle >0° relative to thesurface normal, can be chosen either to be fixed or it can be changedvia a rotatable optical normal arrangement (subsequently also termedlens system for simplification) and/or via a rotatable beam path of thelaser along the desired contour line or separation surface or-line.

In total, the focal line for forming the desired separation line can beguided in up to five separately moveable axes through the material: twospatial axes (x, y) which fix the penetration point of the focal lineinto the material, two angular axes (theta, phi), which fix theorientation of the focal line from the penetration point into thematerial, and a further spatial axis (z′, not necessarily orthogonal tox, y), which fixes how deeply the focal line extends from thepenetration point on the surface into the material. For the geometry inthe Cartesian coordinate system (x, y, z), see also for example thesubsequently described FIG. 3a . In the case of the perpendicularincidence of the laser beam on the substrate surface, z=z′ applies.

The final separation of the material (separation of the contour) alongthe produced contour line is effected either by inherent stress of thematerial or by introduced forces, e.g. mechanically (tension) orthermally (non-uniform heating/cooling). Since in steps (a), (b) and (d)no material is ablated, there is generally initially no continuous gapin the material but only a highly disrupted fracture surface(microcracks) which are interlocked per se and possibly also connectedby bridges. As a result of the forces introduced subsequently in theaftertreatment step, the remaining bridges are separated via lateral(effected parallel to the substrate plane) crack growth and theinterlocking is overridden so that the material can be separated alongthe separation surface.

The laser beam focal line which can be used in (a), (b) and (d) istermed, for simplification previously and subsequently, also focal lineof the laser beam. In (a), (b) and (d), the substrate is prepared by thecrack formation (induced absorption along the focal line which extendsperpendicular to the substrate plane) with the contour line, thecrackline portions and the stress-relieving line portion(s) forseparation of the contour from the substrate. The crack formation iseffected preferably perpendicular to the substrate plane into thesubstrate or into the interior of the substrate (longitudinal crackformation). As described already, generally a large number of individuallaser beam focal lines must be introduced into the substrate along oneline (e.g. contour line) on the substrate surface in order that theindividual parts of the substrate can be separated from each other. Forthis purpose, either the substrate can be moved parallel to thesubstrate plane relative to the laser beam or to the optical arrangementor, conversely, the optical arrangement can be moved parallel to thesubstrate plane relative to the substrate which is disposed in astationary manner.

The induced absorption of steps (a), (b) and (d) is advantageouslyproduced such that the crack formation in the substrate structure iseffected without ablation and without melting of the substrate material.This takes place by means of adjusting the already described laserparameters, explained subsequently also in the scope of examples, andalso the features and parameters of the optical arrangement. Theextension 1 of the laser focal line and/or the extension of the portionof the induced absorption in the substrate material (in the substrateinterior) respectively, viewed in the beam longitudinal direction, canthereby be between 0.1 mm, preferably between 0.3 mm and 10 mm. Thelayer thickness of the substrate is preferably between 30 and 3,000 μm,particularly preferred between 100 and 1,000 μm. The ratio 1/d of thisextension 1 of the laser beam focal line and the layer thickness d ofthe substrate is preferably between 10 and 0.5, particularly preferredbetween 5 and 2. The ratio L/D of the extension 1 of the portion of theinduced absorption in the substrate material, viewed in the beamlongitudinal direction, and of the average extension D of the portion ofthe induced absorption in the material, i.e. in the interior of thesubstrate, is preferably, viewed transversely relative to the beamlongitudinal direction, between 5 and 5,000, particularly preferredbetween 50 and 5,000. The average diameter δ (spot diameter) of thelaser beam focal line is preferably between 0.5 μm and 5 μm,particularly preferred between 1 μm and 3 μm (e.g. at 2 μm). The pulseduration of the laser should be chosen such that, within the interactiontime with the substrate material, the heat diffusion in this material isnegligible (preferably no heat diffusion is effected). If the pulseduration of the laser is characterised with τ, then there appliespreferably for τ, δ and the heat diffusion constant β of the material ofthe substrate, τ<<δ²/β. This means that τ is less than 1%, preferablyless than 1% of δ²/β. For example, the pulse duration τ at 10 ps (oreven below that) can be between 10 and 100 ps or even above 100 ps. Thepulse repetition frequency of the laser is preferably between 10 and1,000 kHz, preferably at 100 kHz. The laser can thereby be operated as asingle pulse laser or as burst pulse laser. The average laser power(measured on the beam output side of the laser) is preferably between 10watts and 100 watts, preferably between 30 watts and 50 watts for steps(a), (b) and (d).

In steps (a), (b) and (d), a laser beam is hence moved relative to thesubstrate surface along a line, along which a large number of individualzones of internal damage are to be introduced into the substrate (alsotermed extended portions of induced absorption in the interior of thesubstrate along the respective line). The ratio a/δ of the averagespacing a of the centres of immediately adjacent zones of internaldamage, i.e. produced directly after each other (portions of inducedabsorption) and the average diameter δ of the laser beam focal line(spot diameter) is preferably between 0.5 and 3.0, preferably between1.0 and 2.0 (see in this respect also FIG. 4).

The final separation of the contour from the substrate can be effectedby, after steps (a) to (d) (possibly also already during implementationof one of these steps), mechanical forces being exerted on the substrate(for example by means of a mechanical stamp) and/or thermal stressesbeing introduced into the substrate (for example by means of a CO₂laser) in order to heat and cool again the substrate non-uniformly. As aresult, between immediately adjacent extended portions of inducedabsorption or between immediately adjacent zones of internal damage, acrack formation in order to divide the substrate into a plurality ofparts, i.e. for separating the contour can be effected. This crackformation should thereby be understood (in contrast to the depth crackformation induced in the direction of the substrate depth or that insteps (a), (b) and (d), as transverse crack formation, i.e. as a lateralcrack formation in the substrate plane (corresponding to the course ofthe contour line, along which the contour is to be separated from thesubstrate).

It is thereby essential, in the case of this preferred procedure insteps (a), (b) and (d) that, per laser pulse (or per burst pulse), alaser beam focal line (and not merely a focal point which is notextended or only very locally) is produced. For this purpose, the laserlens systems illustrated also in detail subsequently are used. The focalline thus determines the zone of interaction between laser andsubstrate. If the focal line falls at least in portions (viewed in thedepth direction) into the substrate material to be separated, then thelaser parameters can be chosen such that an interaction with thematerial takes place, which produces a crack zone along the entire focalline (or along the entire extended portion of the laser beam focal linewhich falls into the substrate). Selectable laser parameters are forexample the wavelength of the laser, the pulse duration of the laser,the pulse energy of the laser and also possibly the polarisation of thelaser.

As a result of this preparation of the contour separation in steps (a),(b) and (d), it is made possible according to the invention to separatecontours made of very thin glass substrates (glass substrates withthicknesses <300 μm, <100 μm or even <50 μm. This is effected withoutedges, damage, cracks, flaking or the like on the substrate (remains)which are left after separation of the contour so that complexaftertreatments are not required according to the invention. The zonesof internal damage along the lines can thereby be introduced at highspeeds (>1 m/s).

Further advantageously achievable features of the method according tothe invention are described in claims 9 and 10. There is therebyunderstood by a spiral (claim 10) very much in general (viewed in thesubstrate plane), a planar linear structure which is wound multipletimes within itself and of almost any shape, which structure begins atone point (in the centre of the internal contour) and, with increasingnumber of windings, approaches the outer edge of the internal contourmore and more and hence approximates to the latter (a spiral accordingto the invention is therefore not restricted to mathematical spirals inthe narrower sense).

Claim 11 describes further advantageous features of the invention. Anyfeatures can thereby be produced in any combination with each other. Thelaser properties described in claim 11 apply (provided nothing differentis mentioned) likewise for the production and the beam guidance of thematerial-removing laser beam in the material removal step. With respectto the specific laser parameters in the material removal step which areproduced advantageously, see however claim 12.

It is possible to use the types of laser mentioned in claims 11 and 12as material-removing laser by (in comparison with production of a largenumber of zones of internal damage with these types of laser) the lensconstruction being correspondingly adapted: no focal line lens system isused but instead a “normal” lens with e.g. 100 mm focal distance(preferably in the range between 70 mm and 150 mm). A galvanometerscanner set up with F-theta-lens is preferred.

Further possible lasers: Nd:YAG laser with 532 nm/515 nm wavelength.However, also a CO₂ laser with 9 to 11 μm wavelength together with a gasnozzle is very suitable.

It can prove to be favourable to vary, between step (a), on the onehand, and step(s) (b) and/or (d), on the other hand, e.g. the spacingbetween adjacent zones of internal damage. In particular increasing thisspacing in step(s) (b) and/or (d) is advantageous compared with step (a)since a favourable crack formation and hence damage in the internalregion of an internal contour thus takes place.

Parameters by way of example can be as follows:

-   -   For toughened glass (0.7 mm; DOL 40 μm): burst 2 pulses; 200 kHz        repetition rate; 3.5 μm pulse spacing; 25 W laser power;        numerical aperture lens system 0.1; focal line length 1.8 mm.    -   For untoughened glass (2.8 mm): burst 5 pulses, 100 kHz        repetition rate; 5 μm pulse spacing, 50 W laser power; numerical        aperture lens system 0.08; focal line length 2.8 mm.

Advantageous procedures for implementing the material removal step aredescribed in claims 13 and 14. For example a 20-times passage of theremoval line for a glass substrate of thickness 0.7 mm is therebyeffected in order to cut the removal line into the substrate materialover the entire thickness of the substrate material.

In the procedure according to claim 14, beams of all lasers mentioned inthe present invention can be used as laser beams, with the exception ofa CO₂ laser. In particular, a laser wavelength of 532 nm can be used.Polyoxymethylene (POM) can be used as precipitation material.

The mounting of the substrate can be ensured for example with the helpof a clamping device with a depression as cavity. By means of the vapourpressure in the gas-sealed cavity, expulsion of the substrate pieceseparated by means of the separation line and possibly even expulsion ofthe thereafter still remaining remains of the contour still connected tothe substrate is possible.

Claim 15 advantageously describes materials which can be machined withthe method according to the invention.

Devices according to the invention which are capable of implementing themethods according to the invention are described in claims 16 to 18.

A laser which is capable, according to claim 18, of generating both thelaser beam in steps (a), (b) and (d) and the material-removing laserbeam for the material removal step is for example a 50 W picosecondlaser.

According to the invention, it can be advantageous for the finalseparation of the contour to supply moisture to the substrate materialafter introduction of the large number of zones of internal damage. As aresult of capillary forces, water is drawn into the damage zones and caninduce stresses by means of linking up with open bonds in the glassstructure (caused by the laser), which stresses help finally to form acrack. Hence controlled supply of the cut contours (internal andexternal contour) with water is possible, the impingement being able tobe effected during or after the laser machining. Use of an evaporator inthe device for producing a moist airflow and/or use of a moist substratemounting or receiving means is possible. A water reservoir can beprovided in the region of the contour line to be introduced.

The present invention of producing and separating a contour in or from aplanar substrate has the following advantages in particular relative tothe contour cutting methods known from the state of the art:

-   -   By combining the introduction of zones of internal damage, on        the one hand (steps (a), (b) and possibly also (d)), and the        material removal-and/or material deformation step (c), on the        other hand, a very high separation quality can be achieved for        contours: practically no break-outs occur, the cut edges on the        substrate, after removal of the contour, have very low roughness        and also high precision.    -   Internal contours shaped in almost any way (circular internal        contours, oblong hole-shaped internal contours or any free form        surfaces) can be separated with great precision according to the        invention. A high resolution of structures of the internal        contour is thereby possible.    -   The formation of stress cracks outside the internal contour        (i.e. in the remaining substrate) is avoided.    -   The method is suitable not only for removing internal contours        but also for separating external contours, which have very small        radii or corners, with very good quality of the produced        external edges on the remaining substrate. In particular,        external contours which have undercuts (e.g. dovetail-shaped        external contours) can be produced and separated with high        quality.

Subsequently, the present invention is described with reference toembodiments. The material removal-and/or material deformation step whichis implemented here as material removal step is designated here in briefwith (c). There are shown:

FIG. 1: The principle of positioning according to the invention of afocal line, i.e. the machining of the substrate material which istransparent for the laser wavelength based on induced absorption alongthe focal line in steps (a), (b) and (d).

FIG. 2: An optical arrangement which can be used according to theinvention for steps (a), (b) and (d).

FIGS. 3a and 3b : A further optical arrangement which can be usedaccording to the invention for steps (a), (b) and (d).

FIG. 4: A microscope image of the substrate surface (plan view on thesubstrate plane) of a glass disc machined according to step (a).

FIGS. 5a to 5d : Steps (a) to (d) which lead to removal of a circularinternal contour from a substrate according to the invention.

FIG. 6: An example of step (d) according to the invention in which astress-relieving spiral is produced as stress-relieving line portion.

FIG. 7: An example of separation according to the invention of anexternal contour from a substrate.

FIG. 8: Examples of different cut guidances for removing a circularinternal contour.

FIG. 9: An example for implementing a material removal step.

FIG. 10: A sketch of a device according to the invention for producingand separating contours.

FIG. 1 outlines the basic procedure of steps (a), (b) and (d). A laserbeam 3 which is emitted by the laser 12 (FIG. 10), not shown here, andwhich is designated on the beam input side of the optical arrangement 20with the reference number 3 a, is beamed onto the optical arrangement 20of the invention. The optical arrangement 20 forms, from the radiatedlaser beam, on the beam output side over a defined extension regionalong the beam direction (length 1 of the focal line), an extended laserbeam focal line 3 b. Covering the laser beam focal line 3 b of the laserradiation 3 at least in portions, the planar substrate 2 to be machinedis positioned in the beam path after the optical arrangement. Thereference number 4 v designates the surface of the planar substrateorientated towards the optical arrangement 20 or the laser, thereference number 4 r designates the rear-side surface of the substrate 2which is normally parallel hereto and at a spacing therefrom. Thesubstrate thickness (perpendicular to the surfaces 4 v and 4 r, i.e.measured relative to the substrate plane) is designated here with thereference number 10.

As FIG. 1a shows, the substrate 2 here is orientated perpendicular tothe beam longitudinal axis and hence to the focal line 3 b which isproduced in space by the optical arrangement 20 behind the same (thesubstrate is perpendicular to the drawing plane) and, viewed along thebeam direction, is positioned relative to the focal line 3 b such thatthe focal line 3 b, viewed in the beam direction, begins in front of thesurface 4 v of the substrate and ends in front of the surface 4 r of thesubstrate, i.e. still inside the substrate. The extended laser beamfocal line 3 b hence produces (with suitable laser intensity along thelaser beam focal line 3 b which is ensured by the focusing of the laserbeam 3 on a portion of the length 1, i.e. through a line focus of length1) in the overlapping region of the laser beam focal line 3 b with thesubstrate 2, i.e. in the material of the substrate which is covered bythe focal line 3 b, an extended portion 3 c, viewed along the beamlongitudinal direction, along which an induced absorption in thematerial of the substrate is produced, which induces a crack formationin the material of the substrate along the portion 3 c. The crackformation is thereby effected not only locally but over the entirelength of the extended portion 3 c of the induced absorption (i.e. thezone of internal damage). The length of this portion 3 c (i.e.ultimately the length of the overlapping of the laser beam focal line 3b with the substrate 2) is provided here with the reference number L.The average diameter or the average extension of the portion of theinduced absorption (or of the regions in the material of the substrate 2which are subjected to the crack formation) is designated here with thereference number D. This average extension D corresponds essentiallyhere to the average diameter 8 of the laser beam focal line 3 b.

As FIG. 1a shows, substrate material which is transparent for thewavelength λ of the laser beam 3 is hence heated according to theinvention by induced absorption along the focal line 3 b. FIG. 3b showsthat the heated material ultimately expands so that a correspondinglyinduced stress leads to the microcrack formation according to theinvention, the stress being greatest on the surface 4v.

Subsequently, concrete optical arrangements 20 which can be used forproducing the focal line 3 b and also a concrete optical construction(FIG. 10) in which these optical arrangements can be used are described.All arrangements or constructions are thereby based on theabove-described ones so that respectively identical reference numbersare used for components or features which are identical or correspond intheir function. Subsequently, respectively only the differences aretherefore described.

Since the separation surface leading ultimately to the separation is orshould be of high quality according to the invention (with respect tobreaking strength, geometric precision, roughness and avoidance ofaftertreatment requirements), the individual focal lines 5-1, 5-2, . . .which are to be positioned along for example the contour line 5 on thesurface of the substrate are produced as described with the subsequentoptical arrangements (the optical arrangement is subsequently alsotermed alternatively laser lens system). The roughness is therebyproduced in particular from the spot size or from the spot diameter ofthe focal line. In order to be able to achieve, with a given wavelengthλ of the laser 12 (interaction with the material of the substrate 2), alow spot size of for example 0.5 μm to 2 μm, generally specificrequirements are placed on the numerical aperture of the laser lenssystem 20. These requirements are fulfilled by the subsequentlydescribed laser lens systems 20.

In order to achieve the desired numerical aperture, the lens system musthave, on the one hand, the required opening at a given focal distance,according to the known formulae of Abbé (N.A.=n sin (theta), n:refractive index of the glass to be machined, theta: half the openingangle; and theta=arctan (D/2f); D: opening, f: focal distance). On theother hand, the laser beam must illuminate the lens system up to therequired opening, which is effected typically by beam expansion by meansof expanding telescopes between laser and focusing lens system.

The spot size should thereby not vary too greatly for a uniforminteraction along the focal line. This can be ensured for example (seeembodiment below) by the focusing lens system being illuminated only ina narrow, annular region by the beam then opening and hence thenumerical aperture of course changing only slightly as a percentage.

According to FIG. 2 (cut perpendicular to the substrate plane at thelevel of the central beam in the laser beam bundle of the laserradiation 12; here also, radiation of the laser beam 3 is effectedperpendicular to the substrate plane so that the focal line 3 b or theextended portion of the induced absorption 3 a is parallel to thesubstrate normal), the laser radiation 3 a emitted by the laser 3 isdirected firstly onto a circular diaphragm 20 a which is completelynon-transparent for the laser radiation used. The diaphragm 20 a isthereby orientated perpendicular to the beam longitudinal axis andcentred on the central beam of the illustrated beam bundle 3 a. Thediameter of the diaphragm 20 a is chosen such that the beam bundles(designated here with 3 aZ) which are situated close to the centre ofthe beam bundle 3 a or of the central beam impinge on the diaphragm andare absorbed completely by the latter. Merely beams situated in theexternal circumferential region of the beam bundle 3 a (edge beams,designated here with 3 aR) are not absorbed on the basis of thediaphragm size which is reduced in comparison with the beam diameter butrather pass through the diaphragm 20 a at the side and impinge on theedge regions of the focusing optical element of the optical arrangement20 which is configured here as a spherically ground, bi-convex lens 20b.

The lens 20 b centred on the central beam is configured heredeliberately as uncorrected, bi-convex focusing lens in the form of anormally spherically ground lens. In other words, the sphericalaberration of such a lens is deliberately made use of. As an alternativethereto, aspherical lenses or multilenses which deviate from ideallycorrected systems and have in fact no ideal focal point but rather forma pronounced longitudinally extended focal line of a defined length canbe used (i.e. lenses or systems which have in fact no longer anyindividual focal point). The zones of the lens hence focus precisely asa function of the spacing from the centre of the lens along a focal line3 b. The diameter of the diaphragm 20 a transversely relative to thebeam direction is here approx. 90% of the diameter of the beam bundle(beam bundle diameter defined by the extension up to reduction to 1/e)and approx. 75% of the diameter of the lens of the optical arrangement20. According to the invention, hence the focal line 3 b of anon-aberration-corrected spherical lens 20 is used and was produced bystopping down the beam bundles in the centre. The section is representedin a plane through the central beam, the complete three-dimensionalbundle is produced if the represented beams are rotated about the focalline 3 b.

An improved optical arrangement 20 which can be used according to theinvention is produced if this comprises both an axicon and a focusinglens.

FIG. 3a shows such an optical arrangement 20 in which, viewed in thebeam path of the laser 12 along the beam direction, firstly a firstoptical element with a non-spherical free surface which is shaped toform an extended laser beam focal line 3 b is positioned. In theillustrated case, this first optical element is an axicon 20 c with 5°cone angle which is positioned perpendicular to the beam direction andcentred on the laser beam 3. An axicon or cone prism is a special,conically ground lens which forms a point source on a line along theoptical axis (or even annularly transforms a laser beam). Theconstruction of such an axicon is basically known to the person skilledin the art; the cone angle here is for example 10°. The cone tip of theaxicon thereby points in the opposite direction to the beam direction.In the beam direction at the spacing z1 from the axicon 20 c, a second,focusing optical element, here a plano-convex lens 20 b (the curvatureof which points towards the axicon) is positioned. The spacing z1 atapprox. 300 mm is chosen here such that the laser radiation formed bythe axicon 20 c impinges annularly on the externally situated regions ofthe lens 20 d. The lens 20 d focuses the annularly impinging radiation,on the beam output-side, at a spacing z2 of here approx. 20 mm from thelens 20 d onto a focal line 3 b of a defined length of here 1.5 mm. Theeffective focal distance of the lens 20 d is here 25 mm. The annulartransformation of the laser beam due to the axicon 20 c is provided herewith the reference number SR.

FIG. 3b shows the configuration of the focal line 3 b or of the inducedabsorption 3 c in the material of the substrate 2 according to FIG. 3ain detail. The optical properties of the two elements 20 c, 20 d andalso the positioning of the same is effected here such that theextension 1 of the focal line 3 b in the beam direction correspondsexactly to the thickness 10 of the substrate 2. Correspondingly, exactpositioning of the substrate 2 along the beam direction is necessary inorder, as shown in FIG. 3b , to position the focal line 3 b exactlybetween the two surfaces 4 v and 4 r of the substrate 2.

According to the invention, it is hence advantageous if the focal lineis formed at a specific spacing of the laser lens system and if thelarge part of the laser radiation is focused up to a desired end of thefocal line. This can be achieved, as described, by a mainly focusingelement 20 d (lens) being illuminated only annularly on a desired zone,as a result of which the desired numerical aperture, on the one hand,and hence the desired spot size is produced, however, on the other hand,loses intensity after the desired focal line 3 b of the dispersingcircle over a very short distance in the centre of the spot since anessentially annular spot is formed. Hence the crack formation, in thesense of the invention, is stopped inside a short distance at thedesired depth of the substrate. A combination of axicon 20 c and focalline 20 d fulfils this requirement. The axicon 20 c hereby acts in twoways: by means of the axicon 20 c, a usually round laser spot istransmitted annularly towards the focusing lens 20 d and theasphericality of the axicon 20 c has the effect that, instead of a focalpoint in the focal plane of the lens, a focal line outside the focalplane is formed. The length 1 of the focal line 3 b can be adjusted viathe beam diameter on the axicon. The numerical aperture along the focalline can be adjusted in turn via the spacing z1 axicon-lens and via thecone angle of the axicon. In this way, the entire laser energy can hencebe concentrated in the focal line.

Should the crack formation (in the zone of internal damage) stop, in thesense of the invention, apart from the exit side of the substrate, thenthe annular illumination still continues to have the advantage that, onthe one hand, the laser power is used as well as possible since a largepart of the laser light remains concentrated at the desired length ofthe focal line and, on the other hand, by means of the annularilluminated zone together with the desired aberration adjusted by theother optical functions, a uniform spot size along the focal line can beachieved and hence a uniform separation process according to theinvention along the focal line.

Instead of the plano-convex lens illustrated in FIG. 3a , also afocusing meniscus lens or another more highly corrected focusing lens(aspherical, multilenses) can be used.

Borosilicate- or soda lime glasses 2 without other colouration (inparticular with a low iron content) are optically transparent fromapprox. 350 nm to approx. 2.5 μm. Glasses are generally poor heatconductors, for which reason laser pulse durations of a few nanosecondsdo not in fact allow any substantial heat diffusion out of a focal line3 b. Nevertheless, even shorter laser pulse durations are advantageoussince, with sub-nanosecond-or picosecond pulses, a desired inducedabsorption can be achieved more easily via non-linear effects (intensitysubstantially higher).

For separation of planar glasses according to the invention, for examplea commercially available picosecond laser 12 which has the followingparameters is suitable: wavelength 1,064 nm, pulse duration of 10 ps,pulse repetition frequency of 100 kHz, average power (measured directlyafter the laser) of up to 50 W. The laser beam firstly has a beamdiameter (measured at 13% of the peak intensity, i.e. 1/e² diameter of aGaussian beam bundle) of approx. 2 mm, the beam quality is at leastM²<1.2 (determined according to DIN/ISO 11146 ). With a beam expandinglens system (commercially available beam telescope according to Kepler),the beam diameter can be increased by the factor 10 to approx. 20-22 mm.With a so-called annular diaphragm 20 a of 9 mm diameter, the inner partof the beam bundle is stopped down so that an annular beam is formed.With this annular beam, e.g. a plano-convex lens 20 b with 28 mm focaldistance (quartz glass with radius 13 mm) is illuminated. By means ofthe strong (desired) spherical aberration of the lens 20 b, the focalline according to the invention is produced.

The theoretical diameter δ of the focal line varies along the beam axis,for this reason it is advantageous for the production of a homogeneouscrack surface if the substrate thickness 10 is less here than approx. 1mm (typical thicknesses for display glasses are 0.5 mm to 0.7 mm). Witha spot size of approx. 2 μm and a spacing of spot to spot of 5 μm, aspeed of 0.5 m/sec is produced, with which the focal line can be guidedover the substrate 2 along the contour line 5 (cf. FIG. 4). With 25 Waverage power on the substrate (measured following the focusing line 7),there results from the pulse train frequency of 100 kHz, a pulse energyof 250 μJ which can also be effected in a structured pulse (rapid trainof individual pulses at a spacing of only 20 ns, so-called burst pulse)of 2 to 5 sub-pulses.

Untoughened glasses essentially have no internal stresses, for whichreason the disruption zone which is still interlocked and connected byunseparated bridges still at first holds the parts together withoutexternal effect. If however a thermal stress is introduced, the contour1 is finally completely separated and without further externalintroduction of force from the substrate 2. For this purpose, a CO₂laser with up to 250 W average power is focused on a spot size ofapprox. 1 mm and this spot is guided at up to 0.5 m/s over the contourline 5, the crack lines 6 and possibly also the stress-relieving line11(cf. FIGS. 5a to 5d ). The local thermal stress due to the introducedlaser energy (5 J per cm of the lines) separates the contour 1completely.

For separation in thicker glasses, the threshold intensity for theprocess (induced absorption and formation of a disruption zone bythermal shock) must of course be achieved via a longer focal line 1.Hence higher required pulse energies follow and higher average powers.With the above-described lens system construction and the maximumavailable laser power (after losses due to the lens system) of 39 W onthe substrate, the separation of approx. 3 mm thick glass is achieved.On the one hand, the annular diaphragm 20 a is thereby removed and, onthe other hand, the spacing of lens 20 b to substrate is corrected(nominal focal spacing increases in direction) such that a longer focalline is produced in the substrate.

Subsequently, a further embodiment for separating toughened glass ispresented.

Sodium-containing glasses are toughened by sodium being exchanged forpotassium on the glass surface by immersion in liquid potassium saltbaths. This leads to a considerable internal stress (compression stress)in a 5-50 μm thick layer on the surfaces, which in turn leads to higherstability.

Basically, the process parameters during separation of toughened glassesare similar to those with untoughened glasses of a comparable dimensionand composition. However, the toughened glass can shatter very much moreeasily as a result of the internal stress and in fact as a result ofundesired crack growth which is effected not along the lasered intendedfracture surface 5 but into the material. For this reason, the parameterfield for successful separation of a specific toughened glass isspecified more tightly. In particular the average laser power and theassociated cutting speed must be maintained very exactly and in fact asa function of the thickness of the toughened layer. For a glass with 40μm thick toughened layer and 0.7 mm total thickness, there results withthe above-mentioned construction for example the following parameters:cutting speed of 1 m/s at 100 kHz pulse train frequency, therefore aspot spacing of 10 μm, with an average power of 14 W. In addition, thestep sequence (a) to (c) (preferably with (d)) for such glasses isparticularly crucial in order to prevent undesired cracks anddestruction in the remaining substrate 2.

Very thin toughened glasses (<100 μm) consist predominantly of temperedmaterial, i.e. front-and rear-side are for example respectively 30 μmsodium-depleted and hence toughened and only 40 μm in the interior areuntoughened. This material shatters very easily and completely if one ofthe surfaces is damaged. Such toughened glass films have to date notbeen machinable in the state of the art but are with the presentedmethod.

Separation of this material according to the method of the invention issuccessful if a) the diameter of the focal line is very small, e.g. lessthan 1 μm, b) the spacing from spot to spot is low, e.g. between 1 and 2μm, and c) the separation speed is high enough so that the crack growthcannot run ahead of the laser process (high laser pulse repetitionfrequency, e.g. 200 kHz at 0.2 to 0.5 m/s).

FIG. 4 shows a microscopic image of the surface of a glass disc machinedaccording to the invention according to step (a). The individual focallines or extended portions of induced absorption 3 c along the contourline 5 which are provided here with the reference numbers 5-1, 5-2, . .. (into the depth of the substrate perpendicular to the illustratedsurface) are connected along the line 5, along which the laser beam wasguided over the surface 4 v of the substrate, to form a separationsurface by crack formation for separation of the substrate parts whichis effected via the further steps according to the invention. Readilyseen is the large number of individual extended portions of inducedabsorption 5-1, 5-2, . . . , the pulse repetition frequency of thelaser, in the illustrated case, having been coordinated to the feedspeed for moving the laser beam over the surface 4 v such that the ratioa/δ of the average spacing a of immediately adjacent portions 5-1, 5-2,. . . and of the average diameter δ of the laser beam focal line isapprox. 2.0.

FIGS. 5a -5d show, by way of example, the machining according to theinvention of a 0.7 mm thick glass substrate 2 in plan view on thesubstrate plane.

As FIG. 5a shows, in the contour definition step (a), the laser beam 3of a Nd:YAG laser with a wavelength lambda of 1,064 μm (the laser 12 isnot shown here) is radiated vertically onto the substrate plane andguided along the contour line 5 which characterises the contour 1 to beproduced. The contour 1 to be produced is here a circular internalcontour which is intended to be removed from the substrate 2. The aim ofthe machining is hence the production of an exactly circular hole in thesubstrate 2. The circular internal contour 1 or the substrate materialof the same can be destroyed during method steps (a) to (d) since theremaining substrate portions 2 represent the desired production product.

As FIG. 5a shows, due to the pulse operation of the laser 12 by means ofthe laser beam 3 along the contour line 5, a large number of individualzones 5-1, 5-2, . . . of internal damage is produced in the substratematerial (portions of induced absorption along a portion which isextended, viewed in the beam direction, of the laser beam focal lineproduced by means of the laser). The individual zones of internal damageare thereby produced as described for FIG. 4 (this applies also to thesteps (d) and (b) which are also described subsequently).

After such zones of internal damage 5-1, 5-2, . . . have been producedover the entire circle circumference 5, a fracture line corresponding tothe internal contour 1 to be separated has in fact been produced in thesubstrate, however the material of the internal contour 1, as describedalready, is not yet completely separated from the material of theremaining substrate portion 2. The further steps (b) to (d) now serve toseparate completely the material of the internal contour 1 from thesubstrate 2 such that any damage (such as cracks, flaking and the like)in the remaining substrate material are avoided.

In order to achieve this, there is introduced firstly, in astress-relieving step (d) subsequent to step (a), cf. FIG. 5b (in whichthe features already described in FIG. 5a are provided with identicalreference numbers; this then also applies to the subsequent FIGS. 5c and5d ), a stress-relieving line portion 11 which approximates to thecourse of the contour line 5 (here by a constant spacing from thelatter), is introduced concentrically within the contour line 5 and at aspacing from the latter, i.e. in the material of the internal contour 1.Introduction of the stress-relieving line portion 11 which is likewisecircular here is thereby effected by means of the laser 12 with the samelaser parameters as for the contour line 5 so that, along the completecircular circumference of the portion 11, respectively a large number ofindividual zones 11-1, 11-2, . . . of internal damage is produced in thesubstrate material. The introduction of these zones is also effected asdescribed for FIG. 4.

This step (d) serves to produce a stress reduction, i.e. latent stressesin the substrate material introduced during introduction of the contourline could otherwise lead to tearing of the entire substrate in the caseof small contour radii and highly tempered glasses. This can beprevented by the additional cut of step (d) which is not however anabsolute necessity. This step can have a spiral as shape but can also beconfigured as “circle-within-circle” which approximates to the contourline. The aim of this cut is to minimise the spacing of thestress-relieving line portion 11 relative to the target contour in orderto leave behind as little material as possible and therefore to enableor to promote self-detachment. For example, values for the maximumapproximation of the stress-relieving line portion 11 to the contourline 5 are here approx. 20 μm to 50 μm.

FIG. 5c shows the crack definition step (b) implemented according to theinvention after the stress-relieving step (d). In this step, the laserbeam 3 of the laser 12 is guided, just as in steps (a) and (d), over thesubstrate surface or the internal contour surface so that, here also, alarge number of individual zones 6-1, 6-2, . . . of internal damage isintroduced, as shown in FIG. 4, along the structures 6 inscribed intothe internal contour 1.

As FIG. 5 shows, there are produced, in addition, a plurality of linearcrack line portions 6 a, 6 b, . . . which begin at a place on thecontour line 5, lead away from the contour line 5 respectively at anangle a of here 25° and lead into the contour 1 to be separated.Respectively exactly two crack line portions (for example the crack lineportions 6 a and 6 b) thereby begin at one and the same place on thecontour line 5 and extend in oppositely situated directions respectivelyat the angle α into the inner contour 1 until they cut the previouslyintroduced stress-relieving line portion 11. The angle α is here theangle between the tangent to the contour line 5 at that place at whichthe two crack line portions, which lead from this place, in essentiallyopposite directions, into the material of the internal contour 1 (forexample the portions 6 a and 6 b or also the portions 6 c and 6 d),begin, and the tangent to the respective crack line portion at thisplace (or the crack line portion itself since this coincides with thetangent thereof).

In the above-described way, there is produced, along the entirecircumference of the contour line 5, a plurality of V-shaped crack lines6V which consist respectively of precisely two crack line portions whichbegin at one and the same place on the contour line 5, lead away fromthe contour line 5 over the surface portions of the internal contour 1which are situated between said contour line and the stress-relievingline portion 11, cut the stress-relieving line portion 11 and lead intothe region of the internal contour 1 situated within thestress-relieving line portion 11. Both legs of one and the same V-shapedcrack line 6V thereby lead along the tangent to the contour line 5 atthe place of the tip of the respective crack line, viewed symmetricallyto the normal, towards this tangent, i.e. on both sides of the normal,into the internal contour 1. Smaller angles α of for example α=10° oreven larger angles of for example a α=35° are possible according to thecircular circumference of the lines 5 and 11 and also the spacing ofthese two circular lines from each other.

The crack line portions 6 a, 6 b, . . . need not thereby definitely,even if this is preferred, begin immediately at one place on the contourline 5 but rather can begin also slightly at a spacing from the contourline 5 at a place situated within the internal contour material 1 andcan be guided beyond the stress-relieving line portion 11 into thematerial portion situated within the same (the angle α between theimaginary continued cut line of the respective crack line portion withthe contour line 5, on the one hand, and the tangent to the contour line5, on the other hand, is then calculated).

In the above-described way, preferably five to ten V-shaped crack linesalong the circumference of the circular lines 5, 11 are produced.

The crack lines 6V or the crack line portions 6 a, 6 b, . . . of thesame are thereby placed and orientated preferably such that thedetachment behaviour is improved during and/or after thematerial-removing laser step (c). The material ring remaining after thematerial-removing laser step (c) is specifically segmented such thatindividual segments of the circular ring can be detached more easily. Itis attempted to build up an internally directed stress into the V cutsso that the partial segments after the material-removing laser step (c)are pressed inwards as far as possible by themselves. These V cuts arenot however not an absolute necessity since the method according to theinvention can also function without these.

It is hence essential that some of the ring material portions which areinscribed with the V-shaped crack lines into the material of thecircular ring portion between the two structures 5 and 11 (here: theapproximately triangular portions between the two legs of one and thesame V-shaped crack line) could move towards the centre of the internalcontour 1 (if they were already completely detached by means of thezones 6-1, 6-2, . . . ) without interlocking with adjacent ring materialportions.

FIG. 5d finally shows the material removal step (c) after the crackdefinition step (b). (In FIG. 5d , merely three of the V-shaped cracklines introduced in step (b) are illustrated for reasons of clarity).

In step (c), a material-removing laser beam 7 produced by a laser 14,not shown here, is directed towards the substrate surface. In comparisonwith introduction of the large number of zones of internal damage insteps (a), (b), (d), as described for FIG. 4, the parameters of thematerial-removing laser beam 7 differ from the laser beam 3 as follows:a point focus or point damage with accompanying material removal isapplied. Wavelength: between 300 nm and 11,000 nm; particularly suitable532 nm or 10,600 nm. Pulse durations: 10 ps, 20 ns or even 3,000 μs.

As FIG. 5d shows, with the laser beam 7 within the stress-relieving lineportion 11, a removal line 9 which extends here likewise annularly andalong the entire circumference of the contour circle 5 or of thestress-relieving line circle 11 (shown here merely in sections) isinscribed into the material of the internal contour 1. In the radialdirection (viewed towards the centre of the internal contour 1), thespacing of the removal line 9 from the stress-relieving line 11 is hereapprox. 25% of the spacing of the stress-relieving line 11 from theoutwardly situated contour line 5. The spacing 8 of the removal line 9from the contour line 5 is hence 1.25 times the spacing of thestress-relieving line 11 from the contour line 5. The removal line 9 isthereby introduced such that it still cuts (viewed from the centre ofthe internal contour 1) the inwardly situated ends of the crack lineportions 6 a, 6 b,

After introducing the removal line along the entire circumference of thecontour line 5 or of the stress-relieving line 11, the material portionssituated inside the removal line 9 in the centre of the internal contour1 are detached from the substrate 2 since, along the removal line 9, thesubstrate material is removed over the entire substrate thickness 10(cf. FIG. 9). Hence there remain of the internal contour material 1 tobe separated merely the ring portions situated between the removal line9 and the contour line 5.

Between the edge at the removal line 9, on the one hand, and the contourline 5, on the other hand, approximately triangular ring portions areproduced between the two legs of each V-shaped crack line (see referencenumber 1′) which are in fact interlocked still with the material ofadjacent ring portions (and are characterised here as contour remainsstill to be separated and have the reference number 1 r) but are able tobe removed inwards without introducing stresses which possibly damagethe material of the remaining substrate 2.

In the aftertreatment step which is not shown here (implemented aftersteps (a) to (d)), the remaining undesired contour remains lr (whichalso comprise the stress-relieving portions 1′) are separated from theremaining substrate 2 by means of a mechanical stamp which is moveableperpendicular to the substrate plane.

FIG. 6 shows an alternative form of introducing a stress-relieving lineportion 11 into the substrate material of the internal contour 1 of FIG.5a to be separated. Instead of a single circumferential, circularstress-relieving line portion 11, also a stress-relieving spiral 11Swhich approximates to the course of the contour line 5, is guided fromthe centre of the internal contour 1, viewed radially outwards, woundwithin itself and turning approx. 3.5 times here can be inscribed intothe material of the internal contour 2 to be separated.

As FIG. 7 shows, the present invention can be used not only forseparating closed internal contours 1 from a substrate 2 but also forseparating complexly-shaped external contours 1, the shape of which (cf.for example the dovetail-shaped portion of the contour line 5 in FIG. 7)is such that the external contour 1 of the substrate 2 cannot beproduced with methods known from the state of the art withoutintroducing stress cracks into the remaining substrate material 2. Theangle α of the two oppositely situated legs of the V-shaped crack lines6V-1, 6V-2, . . . which are situated between the contour line 5, on theone hand, and the removal line 9, on the other hand, is here 10°. InFIG. 7, identical or corresponding features designate otherwiseidentical reference numbers as in FIGS. 5a to 5b . The substratethickness perpendicular to the substrate plane is characterised with thereference number 10. The substrate surface orientated towards theincident laser radiation 3, 7 with the reference number 4 v (substratefront-side), the oppositely situated substrate surface (substraterear-side) with the reference number 4 r.

As FIG. 7 shows, introduction of a stress-relieving line portion 11which approximates to the course of the contour line 5 is hence notabsolutely necessary.

The invention can hence be used in particular also for separatingcontours with undercuts.

FIG. 8 shows several different possibilities of how crack line portions6 a, 6 b, . . . , which differ along the course of the contour line 5,begin respectively essentially at the contour line 5 and lead into thematerial of the contour 1 to be separated, can be produced: FIG. 8ashows V-shaped standard crack lines (see also FIG. 5c ). FIG. 8b showsV-shaped multiple crack lines along the contour line course 5 in whichrespectively adjacent V-shaped crack lines intersect at the legsorientated towards each other. FIG. 8c shows open crack lines due tointroduction respectively of only one leg of a V-shaped crack line.

FIG. 9 shows how, with an additional precipitation material 18 (here:polyoxymethylene), the inwardly situated material portion of an internalcontour 1 to be separated, which is completely separated from thesubstrate 2 or from the contour remains 1 r after introducing theremoval line 9 (possibly also with parts of the contour remains 1 rstill adhering undesirably to the substrate 2), can be expelled.Identical reference numbers again designate in FIG. 9 (and also in FIG.10) the features of the invention described already under thesereference numbers.

As FIG. 9 shows, the beam power, which is high compared with the laserbeam 3, of the material-removing laser beam 7 is coupled via a (second,cf. FIG. 10) beam-guiding optical unit 21 onto the substrate 2. Thesubstrate 2 is mounted in a clamping device 16 (e.g. so-called chuck)such that, in a region below the internal contour 1 to be separated, agas-sealed cavity 17 is configured on the substrate rear-side 4 r.

(“Above” is here the substrate front-side 4 v which is orientatedtowards the incident laser beam). Into this cavity 17, the precipitationmaterial 18 was introduced in advance and now is vaporised at thebeginning of the illustrated material removal step (c) by focusing thelaser beam 7 by means of the optical unit 21 through the substrate 2into the cavity 17 (FIG. 9a ). As a result of the laser beam-causedvaporisation, the vaporised precipitation material precipitates on theportion of the substrate rear-side 4 r which is situated in the cavity17 and forms (FIG. 9b ) on at least one surface of the substraterear-side 4 r which corresponds to the internal contour 1 to beseparated, a coupling layer 18′ which improves coupling of the laserbeam 7 into the substrate material. Vaporisation of the material 18 forprecipitation on the rear-side surface 4 r is implemented for approx. .. . seconds. Since the material of the substrate 2 is transparent forthe laser radiation λ, the material of the layer 18′ is however opaquefor λ, coupling of the beam 7 into the substrate material is thusimproved.

Subsequently, the laser radiation 7 is focused 15 by the optical unit 21and through the substrate onto the rear-side surface 4 r (cf. FIG. 9b ).Corresponding to the geometry characterising the removal line 9, thefocal point 15 of the laser radiation 7 is guided by multiple passage ofthe beam 7 along the line 9 successively from the substrate rear-side 4r towards the substrate front-side 4 v in order to remove in successionthe substrate material along the removal line 9, viewed over the entiresubstrate thickness 10, or to vaporise it as a result of the high laserenergy which is introduced. After the large number (e.g. 15 times) ofpassages guided along the contour of the removal line 9 with the focalpoint 15 moving increasingly from the rear-side 4 r to the front-side 4v, finally the material of the internal contour 1 which is situatedinside the removal line 9 (which is illustrated here for simplifiedrepresentation merely once and in the centre above the cavity 17) isdetached and expelled upwards by the vapour pressure prevailing in thecavity 17. With sufficiently high vapour pressure in the cavity 17, alsothe separation of the undesired contour remains lr can be assisted bythis (cf. FIG. 5d ).

FIG. 10 illustrates a device according to the invention for implementingthe method according to the invention, which is provided with a beamproducing-and beam-forming arrangement 19 configured in a common laserhead. The unit 19 comprises the two lasers 12 (for production of thelaser beam 3 which produces the individual zones of internal damage withlower laser intensity) and 14 (for producing the material-removing laserbeam 7 of higher intensity) and also two beam-guiding optical units 20and 21 which have respectively a galvanometer scanner connectedsubsequent to an F-theta lens for beam deflection (the construction ofsuch optical units is known to the person skilled in the art). The laserradiation 3 of the laser 12, focused via the F-theta lens and thegalvanometer scanner of the unit 20, is hence guided towards the surfaceof the substrate 2 and, for producing the contour line 5, is suitablydeflected by means of the galvanometer scanner. Correspondingly, thelaser radiation 7 of the laser 14, focused via the F-theta lens and thegalvanometer scanner of the unit 21, is imaged on the surface of thesubstrate 2 and is deflected in order to produce the removal line 9 bythe galvanometer scanner of the unit 21.

Alternatively, also stationary lens systems can be used instead of usingmoving lens systems (then the substrate is moved).

A central control unit which is configured here in the form of a PC 22with suitable memories, programmes etc. controls the beam production,beam focusing and beam deflection by means of the unit 19 via abidirectional data-and control line 23.

Differences in the beam-guiding lens systems 20 and 21 for producing thetwo different laser beams 3 and 7 are as follows: the laser beam 7 isguided towards the surface in comparison to the beam 3, e.g. with acorrected F-theta lens, which leads to the formation of a point focus.The focal distance of the lens for the beam 7 is significantly greaterthan for the beam 3, e.g. 120 mm in comparison with 40 mm.

1. A method for producing a contour (1) in a planar substrate (2) andfor separating the contour (1) from the substrate (2), in particular forproducing an internal contour (1) in a planar substrate (2) and forremoving the internal contour (1) from the substrate (2), the methodcomprising: a contour definition step (a) wherein a laser beam (3) isguided over the substrate (2) along a contour line (5) defining thecontour (1) to be produced, and producing a plurality of individualzones (5-1, 5-2, . . . ) of internal damage are in the substratematerial, and a material removal- and/or material deformation step (c)performed after the contour definition step (a) by a laser beam guidedover the substrate (2) and/or radiated onto the substrate (2); andsubstrate material is: (i) removed from the substrate (2), and/or (ii)detached from the substrate (2) by material removal and/or by plasticdeformation; and a crack definition step (b) which is performed beforethe material removal-and/or material deformation step (c) and after thecontour definition step (a), by a laser beam (3) which is guided overthe substrate (2), along a plurality of crack line portions (6 a, 6 b, .. . ) which, viewed from the contour line (5), lead away at an angleα>0° and into the contour (1) to be separated, respectively a pluralityof individual zones (6-1, 6-2, . . . ) of internal damage are producedin the substrate material.
 2. The method according to claim 2, whereinthe material removal-and/or material deformation step (c) is performedafter the contour definition step (a) and wherein a material-removinglaser beam (7) is guided over the substrate (2) along a removal line (9)which extends along the contour line (5) but at a spacing (8) from thelatter and also in the contour (1) to be separated, and the substratematerial is removed over the entire substrate thickness (10).
 3. Themethod according to claim 1, such that the material removal- and/ormaterial deformation step (c) is performed after the contour definitionstep (a) and comprises a material deformation step in which, a laserbeam is guided over the contour (1) to be separated and/or radiated ontothe contour (1) to be separated and generating a plastic deformation ofsubstrate material, in particular a CO₂ laser beam, substrate materialof the contour (1) to be separated is thermally deformed such that it isremoved from the substrate (2) and/or detached from the substrate (2).4. The method according to claim 2, wherein the removal line (9) iscrossing the crack line portions (6a, 6b, . . . ).
 5. The methodaccording to claim 1, wherein a stress-relieving step (d) is performedbefore the material removal- and/or material deformation step (c) andbetween the contour definition step (a) and the crack definition step(b) by a laser beam (3) which is guided over the substrate (2), along atleast one stress-relieving line portion (11), which extends in thecontour (1) to be separated and approximates to the course of thecontour line (5), respectively a large number of individual zones (11-1,11-2, . . . ) of internal damage are produced in the substrate material.6. The method according to claim 1, wherein an after treatment stepperformed after the material removal- and/or material deformation step(c), for the complete separation of the contour (1) from the substrate(2), remains (1 r) of the contour (1) which are still possibly connectedto the substrate (2) are separated from the substrate (2) by thermaltreatment of these contour remains (1r) and/or of the substrate (2), inparticular by local non-homogeneous heating by guidance of a CO₂ laserbeam, at least in portions, over the contour line (5), the crack lineportions (6 a, 6 b, . . . ) and/or the stress-relieving line portion(11), and/or such contour remains (1 r) are separated from the substrate(2) by ultrasonic treatment of the contour remains (1 r) and/or of thesubstrate (2) and/or such contour remains (1 r) are separated from thesubstrate (2) by exerting mechanical forces.
 7. The method according toclaim 1, wherein the zones (5-1, 5-2, . . . 6-1, 6-2, . . . , 11-1,11-2, . . . ) of internal damage are produced without ablation andwithout melting of substrate material.
 8. The method according to claim1, wherein at least some of the zones (5-1, 5-2, . . . , 6-1, 6-2, . . ., 11-1, 11-2, . . . ) of internal damage are produced by point focusingof the laser beam (3) into the interior of the substrate material at theplace of the respective zone, and/or at least some of the zones (5-1,5-2, . . . , 6-1, 6-2, . . . , 11-1, 11-2, . . . ) of internal damageare produced by an induced absorption being produced in the substratematerial along, viewed in the beam direction of the laser beam (3), anextended portion (3 c) of a laser beam focal line (3 b), such thatabsorption an induced crack formation along this extended portion (3 c)is effected in the substrate material.
 9. The method according claim 4,wherein a V-shaped crack line (6V) is produced in the crack definitionstep (b) by producing, along two crack line portions (6 a, 6 b) whichlead from one and the same place on the contour line (5) at the sameangle α>0° away from the contour line (5), but, viewed along the contourline (5), in opposite directions into the contour (1) to be separated,respectively a plurality of individual zones (6-1, 6-2, . . . ) ofinternal damage in the substrate material, wherein (i) viewed along thecontour line (5), a plurality of such V-shaped crack lines (6V-1, 6V-2,. . . ) being produced at a spacing from each other, in particular beingproduced over the entire length of the closed contour line (5) of aninternal contour (1) to be separated, and/or (ii) the angle α beingbetween 20° and 40°.
 10. The method according to claim 5, wherein astress-relieving spiral (11S) is produced in the stress-relieving step(d) by, along a stress-relieving line portion (11) which approaches, ina spiral, the closed contour line (5) of an internal contour (1) to beremoved, viewed from the centre of the internal contour (1) to beremoved to the external edge of this internal contour (1), a pluralityof individual zones (11-1, 11-2, . . . ) of internal damage beingproduced.
 11. The method according to claim 1, wherein in the contourdefinition step (a), in the crack definition step (b) and/or in thestress-relieving step (d), laser beams (3) of identical beam propertiesare guided over the substrate (2) and/or in that these laser beams (3)are produced by one and the same laser (12) and are radiated onto thesubstrate (2) by the same beam-forming lens system (20), and/or thewavelength λ of a laser (12) producing at least one of these laser beams(3) is chosen such that the substrate material is transparent or isessentially transparent for this wavelength, there being understood bythe latter that the intensity reduction of the laser beam, effectedalong the beam direction, in the substrate material is, per millimetreof penetration depth, 10% or less, and/or the average diameter δ of atleast one of these laser beams (3), when impinging on the irradiatedsurface of the substrate (2), i.e. the spot diameter δ, is between 0.5μm and 5 μm, and/or the pulse duration τ of a laser (12) producing atleast one of these laser beams (3) is chosen such that, within theinteraction time with the substrate material, the heat diffusion in thesubstrate material is negligible, and/or the pulse repetition frequencyof a laser (12) producing at least one of these laser beams (3) isbetween 10 kHz and 1,000 kHz, and/or a laser (12) producing at least oneof these laser beams (3) is operated as single pulse laser or as burstpulse laser, and/or the average laser power, measured directly at thebeam output side of a laser (12) producing at least one of these laserbeams (3), is between 10 watts and 100 watts.
 12. The method accordingto claim 2, wherein in the material removal step, for example for aglass- or crystal element as substrate (2) which is transparent in thevisible wavelength range, an Nd:YAG laser (14) with a wavelength λ of1,064 nm, or a Y:YAG laser (14) with a wavelength λ of 1,030 nm is usedfor producing the material-removing laser beam (7), and/or the averagediameter of the material-removing laser beam (7), when impinging on theirradiated surface of the substrate (2), i.e. its spot diameter, isbetween 5 μm and 200 μm, and/or the pulse repetition frequency of thelaser (14) producing the material-removing laser beam (7) is between 0.1kHz and 200 kHz, and/or the laser (14) producing the material-removinglaser beam (7) is operated as single pulse laser or as burst impulselaser, and/or the average laser power, measured directly at the beamoutput side of the laser (14) producing the material-removing laser beam(7), is between 10 watts and 200 watts.
 13. The method according toclaim 2, wherein the material removal step is implemented as follows:the wavelength of the material-removing laser beam (7) is chosen suchthat the substrate material is transparent or essentially transparentfor this, the material-removing laser beam (7) is focused through thesubstrate (2) into a focal point (15) situated on the substraterear-side (4 r) which is orientated away from the beam incidence sidesubstrate surface (substrate front-side 4 v) and the material-removinglaser radiation (7) is guided several times along the removal line (9)with successive displacement of the focal point (15) from the substraterear-side (4 r) towards the substrate front-side (4 v) in order toremove the substrate material over the entire substrate thickness (10).14. The method according to claim 13, wherein the following is performedbefore beginning the material removal step: firstly, the substrate (2)is mounted via a mounting (16) such that, in the region of the contour(1) to be separated between the substrate rear-side (4 r) and themounting (16), a gas-sealed cavity (17) is formed, and subsequently, aprecipitation material (18), which has been positioned before mountingof the substrate (2) such that it is situated in the cavity (17) aftermounting of the substrate (2), is vaporised, by a laser beam (3, 7)being focused into the cavity (17).
 15. The method according to claim 1,wherein the contour (1) is produced in a planar glass element, inparticular in a disc made of hardened glass or of unhardened glass, orin a planar crystal element as substrate (2) and is separated therefrom.16. A device for producing a contour (1) in a planar substrate (2) andfor separating the contour (1) from the substrate (2), in particular forproducing an internal contour (1) in a planar substrate (2) and forremoving the internal contour (1) from the substrate (2), comprising: acentral control unit (22) and a beam-producing-and beam-formingarrangement (19) which is configured such that beam production beamfocusing and beam deflection is controlled with the central control unit(22) in such a manner that, (i) in a contour definition step (a) by alaser beam (3) guided over the substrate (2) along a contour line (5)defining the contour (1) to be produced, plurality of individual zones(5-1, 5-2, . . . ) of internal damage in the substrate material areproduced, and (ii) in a material removal-and/or material deformationstep (c) performed after the contour definition step (a) by laser beamguided over the substrate (2) and/or radiated onto the substrate (2),substrate material is removed from the substrate (2) and/or substratematerial is detached from the substrate (2) by material removal and/orby plastic deformation, wherein the beam production, beam focusing andbeam deflection of the beam-producing-and beam-forming arrangement (19)is controlled by the central control unit (22) in such a manner, that ina crack definition step (b) which is performed before the materialremoval- and/or material deformation step (c)) and, by a laser beam (3)which is guided over the substrate (2), along a plurality of crack lineportions (6 a, 6 b, . . . ) which, viewed from the contour line (5),lead away at an angle α>0′ and into the contour (1) to be separated,respectively a plurality of individual zones (6-1, 6-2, . . . ) ofinternal damage are produced in the substrate material.
 17. The deviceaccording to the preceding claim 16, wherein the beam-producing-andbeam-forming arrangement (19) comprises: a first laser (12) producingthe laser beam (3) to be guided in the contour definition step (a), inthe crack definition step (b) and/or in the stress-relieving step (d), asecond laser (14) producing the material-removing laser beam (7) to beguided and/or to be radiated in the material removal- and/or materialdeformation step (c), in particular the laser beam (7) to be guided inthe material removal step, a first beam-guiding optical unit (20) withwhich, in the contour definition step (a), in the crack definition step(b) and/or in the stress-relieving step (d), the laser beam (3) producedwith the first laser (12) can be guided over the substrate (2), and asecond beam-guiding optical unit (21) with which, in the materialremoval- and/or material deformation step (c), the laser beam producedwith the second laser (14), in particular the material-removing laserbeam (7), can be guided over the substrate (2) and/or radiated onto thesubstrate (2).
 18. The device according method claim 16, wherein thebeam-producing-and beam-forming arrangement (19) comprises: a laserproducing, on the one hand, the laser beam (3) to be guided in thecontour definition step (a), in the crack definition step (b) and/or inthe stress-relieving step (d) and, on the other hand, also thematerial-removing laser beam (7) to be guided in the material removalstep, a first beam-guiding optical unit (20) with which, in the contourdefinition step (a), in the crack definition step (b) and/or in thestress-relieving step (d), the laser beam (3) produced with this lasercan be guided over the substrate (2), and a second beam-guiding opticalunit (21) with which, in the material removal step, thematerial-removing laser beam (7) produced with this laser can be guidedover the substrate (2).
 19. The method according to claim 1, wherein thefollowing is performed before beginning the material removal step:firstly, the substrate (2) is mounted via a mounting (16) such that, inthe region of the contour (1) to be separated between the substraterear-side (4 r) and the mounting (16), a gas-sealed cavity (17) isformed, and subsequently, a precipitation material (18), which has beenpositioned before mounting of the substrate (2) such that it is situatedin the cavity (17) after mounting of the substrate (2), is vaporised, bya laser beam (3, 7) being focused into the cavity (17).